(1) Field of the Invention
The present invention relates to transistor devices and, in particular, to those which can be used for microwave oscillators above X band.
The X band is a radio frequency band extending from 5,200 to 10,900 MHz.
(2) Description of the Prior Art
In the prior art, a microwave oscillator uses a transistor device as an oscillating element, which comprises a transistor chip, such as gallium-arsenide Schottky-Barrier gate field-effect transistor (GaAs FET) or silicon (Si) transistor, and a package encapsulating the transistor chip. The package is provided with three terminals, that is, a control terminal, an output terminal, and a ground terminal which is a bottom plate of the package. The transistor chip having three terminals is fixedly mounted on the ground terminal so that one electrode (collector in Si transistor, source in FET) of the transistor chip is directly connected to the ground terminal. The other two electrodes of the chip (base and emitter in Si transistor, gate and drain in FET) are connected to the control terminal and the output terminal by bonding wires, respectively.
Due to inductances of the bonding wires and capacitances of the terminals, an available transistor device for the microwave oscillating element has difficult problems for use in oscillators at a frequency band higher than the X band. That is, it is required for the negative resistance to adjust impedance of external circuit elements connected to the transistor device. Even if the negative resistance can be obtained, the phase rotation is fast so that oscillation cannot be stabilized over a wide frequency band.